From: Kent Sibilev <ksibilev@...>
Date: 2004-03-14T00:21:10+09:00
Subject: Re: Object#clone and Object#dup

Object#dup or Object#clone methods create a shallow copy of the object. 
If you need a deep copy you have to do it either like this:

$ irb
irb(main):001:0> class Klass
irb(main):002:1> attr_accessor :str
irb(main):003:1> def initialize_copy(o)
irb(main):004:2> @str = o.str.dup
irb(main):005:2> end
irb(main):006:1> end
=> nil
irb(main):007:0> s1 = Klass.new
=> #<Klass:0x352bc4>
irb(main):008:0> s1.str = "Hello"
=> "Hello"
irb(main):009:0> s2 = s1.dup
=> #<Klass:0x3452d0 @str="Hello">
irb(main):010:0> s2.str[1,4] = 'i'
=> "i"
irb(main):011:0> s1.str
=> "Hello"
irb(main):012:0> s2.str
=> "Hi"
irb(main):013:0>

or like that:

$ irb
irb(main):001:0> class Klass
irb(main):002:1> attr_accessor :str
irb(main):003:1> end
=> nil
irb(main):004:0> s1 = Klass.new
=> #<Klass:0x35bcc4>
irb(main):005:0> s1.str = "Hello"
=> "Hello"
irb(main):006:0> s2 = Marshal.load(Marshal.dump(s1))
=> #<Klass:0x34ff00 @str="Hello">
irb(main):007:0> s2.str[1,4] = 'i'
=> "i"
irb(main):008:0> s1
=> #<Klass:0x35bcc4 @str="Hello">
irb(main):009:0> s1.str
=> "Hello"
irb(main):010:0> s2.str
=> "Hi"
irb(main):011:0>

Cheers,
Kent.


On Mar 13, 2004, at 8:49 AM, Raphael Bauduin wrote:

> Hi,
>
> I'd like to duplicate n object, work on the copy, and be sure the 
> original
> isn't change at all. How can I do that?
>
> From the pickaxe (example similar to what I'm working on):
>
> class Klass
>    attr_accessor :str
> end
>
> s1 = Klass.new
> => #<Klass:0x4031ad18>
> s1.str = "Hello"
> => "Hello"
> s2 = s1.dup
> => #<Klass:0x4030fcb0 @str="Hello">
> s2.str[1,4] = "i"
> => "i"
>
> s1.str
> => "Hi"
>
> s2.str
> => "Hi"
>
> I would like that s1.str still returns "Hello". I tried with dup and 
> clone,
> with the same result.... What method should I use?
>
> Thanks
>
> Raph
>
>